Repair Methods for Loadbearing Steel Structures Operating on the Norwegian Continental Shelf

Abstract

This paper results from a project initiated by the Petroleum Safety Authority of Norway to describe relevant repair methods for load bearing steel and concrete structures operating on the Norwegian continental shelf. The purpose of the work was to establish a better understanding of repair methods by gathering the experience through decades of oil and gas activities mainly on the Norwegian continental shelf. This paper presents a review of repairs relevant to steel structures. A repair is broadly defined in this paper and includes: The paper includes a brief introduction to government requirements related to petroleum activity on the Norwegian continental shelf. The petroleum industry in Norway is regulated by the Petroleum Safety Authority which further refers to the NORSOK standards and to some extent ISO standards for more detailed principles and guidelines for design and operation of load bearing structures. An important part of a repair project is to uncover the root-cause of the damage or anomaly as this affects how further repair work is to be planned and performed. This often involves analysis that considers the current state of the structure. The results will form the basis for assessing the extent of the problem and whether repair is a necessary measure. In cases where it is concluded that repair is necessary, it needs to be determined the most appropriate repair method. It may also be concluded that repair is not necessary and then it is more appropriate to monitor the condition through an inspection and monitoring program. The repair methods described in this paper are mainly related to fatigue cracks, corrosion and permanent deformation due to overload. Most methods are well known and have been used for decades on the Norwegian continental shelf. The effect and long-term properties can therefore be said to be well known. A few methods where the use is relatively new and where knowledge about the effect and long-term properties can be said to be limited are also presented.